The government announced that it was minded to allow Heathrow to expand. A new runway and sixth terminal will increase capacity from 480,000 to 702,000 flights. The government’s consultation documents – totalling hundreds of pages – did not provide an estimate of the impact on CO2 emissions. In this article, we offer a tentative figure of about 16m tonnes as the potential maximum impact of the proposed expansion. After multiplying by 2.7 to account for the other pollutants created by aviation, the increase takes the total UK emissions from aviation up to 144m tonnes of CO2 equivalent.

The disjunction between government policies on aviation and climate change is startling.

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The aviation industry is making improvements in the fuel consumption of its aircraft. Air traffic control changes are also slightly reducing unnecessary mileage. These two improvements are not happening fast enough to hold down CO2 output. BAA, the operator of the largest UK airports, admits that ‘aviation is growing at a faster rate than technology can reduce emissions’.

Between 1990 and 2005, CO2 output from EU aviation approximately doubled. There is no sign that the rate of increase is declining. The latest figures from the European Environment Agency showed greenhouse gas emissions from air travel up 7.2% in 2005.

Heathrow is the busiest airport in Europe. It uses about 20 million litres of fuel a day. For comparison, motor fuel consumption (petrol + diesel) for the whole of the UK is about 125 million litres a day.

The government now plans to allow a new runway at the airport. This 2,200m strip will run east-west, just south of the M4 motorway. It will be accompanied by a sixth terminal building. These changes are intended to allow the number of aircraft movements to rise from 480,000 to just over 700,000 flights a year. The size of the typical aircraft is also expected to rise so the number of passengers passing through the airport is forecast to go up from 67 million to 128 million.

Number of aircraft movements

Up 46%

Number of passengers handled

Up 91%

Transport Secretary Ruth Kelly said that the new runway is desirable. She said that ‘if nothing changes, Heathrow’s status as a world-class airport will be gradually eroded – jobs will be lost and the economy will suffer.’

The thrust of the government’s opinion is that London’s status as an international business centre will be reduced if its airports fall behind others in Europe. Heathrow is crowded and operates almost at maximum capacity.

The airport owner, Ferrovial, has a slightly different slant on the reasons for expansion. According to a Reuters news report, Ferrovial believes new infrastructure will ‘bring economic benefits through tourism, job creation and businesses relocating to be near Heathrow’. These may be good commercial arguments, but they are not the same as Ruth Kelly’s insistence that Heathrow expansion was critical for the future of the UK.

What will the impact will the new runway have on CO2 emissions?
The new runway and terminal will allow more aircraft to take off and land. Estimating the eventual impact on emissions is difficult:

the extra flights may or may not be larger airplanes than at present

travel distances could be longer or shorter

the new flights could reduce the rate of growth at other airports

aero engine efficiency gains will continue (for new aircraft)

small air traffic routing improvements are possible.

I have therefore assembled three estimates of the CO2 increase arising from Heathrow expansion:

Heathrow has a 22% share of all UK flight movements. I estimate the effect of expansion by assuming that the average extra flight uses the same amount of fuel as the average UK flight today. This is a conservative, or low, estimate because Heathrow flights tend to use big aircraft travelling much longer distances than other airports. This is therefore towards the bottom end of the range of potential impacts. I estimate that this option raises UK CO2 emissions by 3.8m tonnes.

Heathrow has a 29% share of all passenger movements by air from UK airports. If it moves from 69m passengers to its new capacity of 128m passengers, and these extra travellers are typical of the UK as a whole, the extra emissions will be about 9.3m tonnes.

Heathrow’s fuel use today is about half of the total UK aircraft consumption. (This is not incompatible with Heathrow having only 29% of passenger movements – the flights are longer and in bigger aircraft.) If the average Heathrow flight remains as long as it is today and with the same sized aircraft, then if the new capacity is fully used it will increase emissions by about 16m tonnes of CO2.

Today’s UK CO2 emissions from air travel

37.4m tonnes

CO2 increase if extra flights use small amounts of fuel

3.8m tonnes (option 1 above)

CO2 increase if extra flights are similar to current Heathrow number of passengers per flight

9.3m tonnes (option 2 above)

CO2 increase if new capacity is used in the same way (average distances, average plane sizes) as at present

16.0m tonnes (option 3 above)

If option 3 is right, then UK emissions from aviation will rise by almost 50% from today’s levels. This is a pessimistic assumption:

It assumes that the new capacity is used to fly big aircraft long distances (Heathrow’s current pattern).

It assumes that no diversion takes place from other airports and it allows for no increase in engine efficiency.

But it is also easy to imagine circumstances in which the high figure is not far from the truth. The market for long distance travel is increasing fast. More and more people want to visit far-flung places. Aircraft size is getting bigger. The underlying rate of growth in travel is high, so there may be little effect on the business of other airports as a result of the Heathrow expansion.

Air travel in the UK is rising about 5% a year. Let’s assume that the Heathrow expansion takes 10 years to happen. The new capacity can just handle the expected rise in passenger kilometres of travel. If Heathrow were the only airport to expand (which it will not be), then the total impact of the new capacity may well be close to the 16m tonnes figure.

Does this matter?
At the moment, CO2 emissions from aviation are about 6% of the UK total. There is scientific dispute about how the other pollutants created by aircraft in flight should be treated. The IPCC suggests that the CO2 figure should be multiplied by 2.7 to capture the effect of nitrous oxide and other emissions. If we used this figure, current emissions would be about 16% of the UK’s total.

At the moment, international aviation is not included in the emissions ‘inventories’ of Kyoto countries because of the difficulties of allocating the CO2 between states. There is little doubt that the new round of climate change negotiations will bring air travel into any future agreement.

Heathrow expansion could mean that almost all the UK’s total emissions allowance in 2050 is absorbed by aviation. Option 3 calculations suggest that after applying the 2.7 multiplier UK aviation will be up to 144m tonnes of CO2 equivalent. This is just below the figure of 155m tonnes voiced by Gordon Brown as a potential target for the UK in 2050.

Perhaps this is too gloomy a prediction. Engines are getting better and UK airlines will have replaced all their aircraft by 2050. But the scope for improvement is not infinite and continuing growth in plane size will outweigh much of this benefit. Increased prosperity will also create more demand for long-distance travel. The unfortunate truth is that aviation growth and limits on overall UK emissions are extremely difficult to reconcile.

The UK is in a particularly exposed position. In the rest of the EU, emissions from aviation are a much lower percentage of the total. Estimates from the European Environment Agency suggest a figure of something over 3% (not 2% as Ryanair recently reported in a results presentation), so the need to constrain aviation growth is much less pressing elsewhere. If UK plc really is financially dependent on international air travel, then we are in a mess.